Political scientist Randolph L. Braham in 2011 at the Holocaust Memorial Center in Budapest. (Lajos Soos/EPA-EFE/Shutterstock)

In Hungary, the Holocaust began in a flash and seemed to disappear from historical memory just as quickly.

In less than two months in 1944, nearly 400,000 Jews were deported by Hungarian gendarmes working under the Nazi SS. Most were murdered at Auschwitz, the Nazi death camp in Poland, and by the end of World War II, about 600,000 people — two-thirds of Hungary’s Jewish population — had been killed.

Scholarship on that period remained scant for decades, in large part as a result of the repressive policies of communist leader Janos Kadar. It was largely through the efforts of Randolph L. Braham, a political scientist and Holocaust survivor whose parents were killed at Auschwitz, that the plight of Jews in Hungary became far better known.

Dr. Braham did “more for recording the history of the Hungarian Holocaust than anyone else,” Maria M. Kovacs, a history professor at Central European University in Budapest, said while introducing him at a lecture in 2017. “We owe it to him more than to anyone else that this history did not disappear in the Orwellian black hole of forgotten memory.”

Dr. Braham, who described Holocaust scholarship as his “destiny” and fought against moves to whitewash Hungarian collusion with Nazi authorities, was 95 when he died Nov. 25 at his home in Queens. The cause was congestive heart failure, said his son Robert Braham.

A longtime professor at the City University of New York, where he founded the Graduate Center’s Rosenthal Institute for Holocaust Studies and taught for more than three decades at City College in Manhattan, Dr. Braham wrote more than 60 books and hundreds of articles, including many works on comparative politics and the Soviet Union.

He was best known for his 1,600-page, two-volume book “The Politics of Genocide: The Holocaust in Hungary,” described by New York Times reviewer Elenore Lester as one of “the most important works of Holocaust history.”

Originally published in 1981 and now in its third edition, the book set the calamity of the Holocaust against the backdrop of Hungarian politics after World War I, when Jews began to be treated as scapegoats in a country that had lost two-thirds of its territory and was mired in an economic downturn.

At once panoramic and precise, Dr. Braham’s research showed how deportations occurred with astounding speed after the Germans occupied Hungary in March 1944, fearing that the country — an Axis power — would side with the Allies as the war turned against them.

In addition to detailing the actions of Adolf Eichmann, the SS official who oversaw the extermination process, and Hungarian leader Miklos Horthy, a Nazi ally, Dr. Braham focused on lower-level leaders of the roundups and identified those who stood against them.

Among the documents he cited was a letter from a group of Jewish intellectuals in Budapest, who wrote to a Christian group in the city: “But if our beseeching voice, appealing for our bare lives, is in vain, then we only request the Hungarian nation to put an end to our suffering here at home before the deportation with its accompanying horrors and cruelties, so that we can at least be buried in the land of our birth.”

Dr. Braham also wrote and edited wide-ranging studies of the Holocaust in Romania and Ukraine, and testified at war-crimes trials for Holocaust perpetrators even decades after their alleged crimes were committed.

“My function is to pursue the truth,” he told a Canadian jury in the war-crimes trial of Imre Finta, a Hungarian gendarmerie commander who was acquitted in 1990. “I try to comprehend the incomprehensible.”

Randolph Louis Braham was born Adolf Abraham in Bucharest, the capital of Romania, on Dec. 20, 1922, and grew up in Dej, part of Northern Transylvania, which came under Hungarian control in 1940. His father was a laborer, working variously as a farmer and bricklayer, and his mother was a homemaker.

Forbidden to attend high school because he was Jewish, Dr. Braham studied by candlelight, reading writers François Villon and Michel de Montaigne in the original French. He was working as a cabinetmaker’s apprentice when, in 1943, he was drafted into a forced-labor unit in the Hungarian army and sent to the Eastern Front.

As the unit retreated in late 1944, followed closely by the Soviet army, Dr. Braham and four other Jews escaped into the Hungarian forest. With snow falling and military police searching for deserters, they entered a hut in the village of Nyiri, hid under hay piles, and were discovered by a farmer, Istvan Novak.

“Without moving the hay that concealed the fugitives, Novak spoke to the Jews, and in a quiet and gentle voice told them that they had nothing to fear,” according to Yad Vashem, the Israeli Holocaust remembrance center, which honored Novak with the title Righteous Among the Nations for his role in sheltering Dr. Braham and his fellow survivors.

After returning to Dej, Dr. Braham learned that his parents had been deported, along with most of the other Jews in their town. His older sister survived Auschwitz, Robert Braham said in a phone interview, “but they had to perform surgery two days after she was liberated, because she had swallowed pieces of lint and string and stray fabric to keep her stomach full.”

Dr. Braham made his way to American-occupied Berlin, served as a translator in the U.S. Army and immigrated to the United States in 1948; he soon changed his name. That same year, he received a bachelor’s degree in economics and government from City College, where he also received a master’s in education in 1949. He received a doctorate in political science from the New School for Social Research in 1952.

At City College he became chairman of the political science department and retired in 1992. He continued to work at the Rosenthal Institute until his death, and was featured in “The Last Days,” an Oscar-winning 1998 documentary on the Holocaust in Hungary.

In 2013, he published a three-volume “Geographical Encyclopedia of the Holocaust in Hungary,” which chronicled the fate of each Jewish village in that country. “To recommend this work to teachers, their students and researchers is more than an act of friendship,” writer and fellow Holocaust survivor Elie Wiesel wrote in the book’s foreword. “It is the duty of remembrance that belongs to the realm of the sacred.”

Dr. Braham’s wife of 59 years, the former Elizabeth Sommer, a German-born Holocaust survivor, died in 2014. Survivors include his partner, Mary Maudsley of Queens; two sons, Steven Braham of Cortlandt Manor, N.Y., and Robert Braham of Manhattan; and two grandsons.

Dr. Braham made headlines in 2014 when he returned a top Hungarian honor, the Medium Cross of the Order of Merit, and demanded that the Holocaust Memorial Center in Budapest strip his name from its library, which had been dedicated in his honor.

His decision, he said, was a protest of the government’s move to erect a memorial to the German occupation in Hungary, and of efforts that downplayed Horthy’s role in the murder of thousands of Jews.

“I reached this decision with a heavy heart,” Dr. Braham wrote in an open letter. “I . . ., a survivor whose parents and many family members were among the hundreds of thousands of murdered Jews, cannot remain silent, especially since it was my destiny to work on the preservation of the historical record of the Holocaust.”

Correction: An earlier version of this obituary contained several errors, based on information provided by Dr. Braham’s family. The article said he did not receive a college degree; according to school records, he graduated from the City College of New York in 1948 with a major in economics and government. He also received a master’s in education, not political science, according to his personal records. His sister was older, not younger, and Dr. Braham read writers François Villon and Michel de Montaigne in the original French, not Hungarian. The story has been revised.